London: Manchester City won 4-0 at West Bromwich Albion to end Pep Guardiola's worst run as a manager but Jose Mourinho's woes continued as Manchester United's manager was sent to the stands and Ander Herrera sent off in a goalless draw with Burnley at Old Trafford on Saturday.
United, with one goal in four games and a solitary win in seven, must now watch those with Premier League title aspirations pull away.
There were doubles all round at the top as Sergi Aguero and Iikay Gundogan scored twice for City while Alexis Sanchez and Olivier Giroud also struck braces for Arsenal, 4-1 winners at Sunderland. The Gunners have 23 points like league leaders City but are one place behind on goal difference.
Tottenham Hotspur, who play Arsenal next weekend, lost ground after their 1-1 draw with Leicester City while Liverpool were playing in Saturday's late game.
If Guardiola was all smiles after his first win in seven games, there was more frustration for Mourinho who began the start of the second half behind the dug-out before being moved to the directors' box.
The Portuguese had been incensed by the failure of referee Mark Clattenburg to punish Jon Flanagan for a foul on Matteo Darmian but will be equally unhappy with his team who failed to score in 37 attempts, 11 of which were saved by Tom Heaton.
Burnley's keeper produced another excellent performance with a series of outstanding saves, notably from Jesse Lingard and Zoran Ibrahimovic.
Arsenal manager Arsene Wenger was delighted with his team's victory at winless Sunderland, who are experiencing the worst start in Premier League history after 10 games.
The match turned on the introduction of Giroud, who scored with his first two touches as Arsenal netted three times in seven second-half minutes.
Asked whether he deserved credit for the decision to bring on the Frenchman, Wenger said: "The manager gets easy credit when he has quality players on the bench. You do not need to be a special manager to make that decision."
A superb solo goal from Gaston Ramirez helped Middlesbrough to get their first home league win, 2-0 over Bournemouth.
Picking up the ball inside his own half, the Uruguayan forced his way into the Bournemouth area before cutting back inside a defender and scoring.
Hull City remain in the relegation zone after Michael Dawson conceded a late own goal to see the visitors lose 1-0 at Watford.